[JimDirt]

I am having some issue with my jetting lately and cant seem to figure what i am missing

Carb Model 41mm Keihin (all other year CRF450's are 40mm for some reason)
Elevation 2500 ft - 8000 ft
Main Jet 172
Pilot Jet 48
Fuel Screw 3 Turns Out **R&D Flex Jet**

Valves are in Spec

Bike is basically stock with exception of Stock muffler cut down to length of 05 muffler

I have been messing with the jetting TRYING to get it right but for some reason i am off and can't seem to find the right combo

I do NOT want a JD Jetting kit , i should be able to get it dialed with just Pilot and Main and Fuel Screw adjustments , if not , then i am going to just get a newer year carb from EBay , since this 41mm seems to be very temperamental

Issue's:
I tried the stock jetting (45-172) and it needs the fuel screw 3 1/2 or so turns to idle without popping when revving slightly but starts in 1-2 kicks cold with choke

Tried 48 pilot (what is in it now)and it still needs 3 turns to idle without popping when slightly revved , takes several kicks , or slight throttle when kicked to start readily

My main issue is STARTING and IDLING When COLD , it runs fine when running EXCEPT no matter where i set the fuel screw , after say 1 minute of idling it will die or try to unless i raise the idle slightly or rev it once in a while as it will idle fine then just drop the idle dramatically for no reason i can find , but if i blip the throttle every once i a while it will be fine , it just started doing this after i returned from a lower elevation stay (48-180 3 1/2 turns fuel screw jetting 500 ft elevation)

It just does not want to run right (idling/starting issues only) with what should be the proper jetting (45-172 1 1/4 fuel screw)

Any idea's ?? , i have already had the carb off several times, and run cleaner thru it and blew it thoroughly with air with no change , i have checked and cleaned the jets (i have a jet cleaning tool) , and ride it regularly (at least every other week if not every week)using 1 gal of 130 Octane Leaded Av Gas mixed to 5 Gal of Unleaded Premium , i just cant seem to find why with a 45 OR a 48 Pilot , it still needs the Fuel Screw at 3+ turns to start or idle and even then not that great , it runs fine all day , but the starting and idling is just driving me batty
[/b]

[crfsonly]

keep in mind that "jetting" is not just about the proper jets but also the best needle taper. the needle taper is what meters out fuel from the main jet. so, they work together. this is one of the benefits of the JD kit is it includes two custom tapered needles based on actual dyno and field testing with the specific CRF model and model year. since you want to work with the needle you have consider the following:

1. if you go more than 2 3/4 turns out on the fuel screw go up one size on the pilot jet.

2. there are "wear" items in the carb. two that are often overlooked is the emulsion tube or what honda calls the needle jet holder and the needle itself. the needle slides up and down in this tube and will wear both the tube and needle. worn needle and/or tube (more often the tube) you will have these types of symptoms.

3. two other wear items are the floating valve plate and seal. the seal becomes flat or worse and the plate gets worn and no longer functions effectively. the result is less than crisp throttle response and hanging idle. i would start with replacing the seal. we have a how to that will show you the process. both the seal and the plate have a specific orientation.

4. i don't see the reason to mix the gas you are running. have you tried running straight premium pump gas?

5. i recommend installing new jets as part of a process of elimination. it's very difficult to successfully clean pilot jets to new condition. better to eliminate them from the possibilities.

report back with what you find.

ken

[JimDirt]

keep in mind that "jetting" is not just about the proper jets but also the best needle taper. the needle taper is what meters out fuel from the main jet. so, they work together. this is one of the benefits of the JD kit is it includes two custom tapered needles based on actual dyno and field testing with the specific CRF model and model year. since you want to work with the needle you have consider the following:

1. if you go more than 2 3/4 turns out on the fuel screw go up one size on the pilot jet. This is why i made this post because i have gone up 1 size with no difference in results

2. there are "wear" items in the carb. two that are often overlooked is the emulsion tube or what honda calls the needle jet holder and the needle itself. the needle slides up and down in this tube and will wear both the tube and needle. worn needle and/or tube (more often the tube) you will have these types of symptoms.
I have already replaced the Needle Jet as i mentioned in my post , this is not the issue

3. two other wear items are the floating valve plate and seal. the seal becomes flat or worse and the plate gets worn and no longer functions effectively. the result is less than crisp throttle response and hanging idle. i would start with replacing the seal. we have a how to that will show you the process. both the seal and the plate have a specific orientation.
I replaced the seal last year so it should not be worn out already , since the original one lasted 10 years without issue and it changed nothing when i replaced it then (i found the issue was as i had mentioned , a worn Needle Jet)

4. i don't see the reason to mix the gas you are running. have you tried running straight premium pump gas?
The gas mix is to prevent the gas going bad in a month because of all the crappy Ethanol

5. i recommend installing new jets as part of a process of elimination. it's very difficult to successfully clean pilot jets to new condition. better to eliminate them from the possibilities.

The jets that are in there now are new , and i also cleaned them to make sure that there was no dirt in them or the carb itself , again , that is why i posted , i have done all that should need be to make it run using the correct jets , yet even going up did not change the 3 turn symptom for the fuel screw which seems to be the reason it will not start or idle correctly , this is where i need help

report back with what you find.

ken

I have tried all the "common" remedies with no benefit , that is why i posted , i cant think of anything i missed that SHOULD have fixed the issue , in other words , What could make the fuel screw have to be at 3+ turns with a #45 pilot and a #48 , this does not make sense , anything lower than 3 turns and it pops and bangs like its too lean , i can't find any blockage , and everything i can see is clear as far as i can tell , i have several size main jets , and 2 sizes of pilot , all are new and i have tried several combos , at my elevation it should be 45-172-175 , the main should not affect the idle issue so the difference from 172 to 175 should not affect my settings that i am aware of

The needle does not appear to be worn that i can see , the needle jet is new enough and did not have the same symptoms that i am having now when i replaced it , the idle would go up and stay , until i reset it , then it would not idle high enough and stall , at this moment my bike idles fine , for almost a minute then the idle drops dramatically , if i rev it , it will do the same again , and it should not have to be at 3 turns to not pop and backfire like a lean condition , this is where i am at a loss

[crfsonly]

if you used carb cleaner that hit the slide you damaged your floating valve seal. so at the very least replace it. if you removed the slide verify the plate is in the correct orientation. you won't be able to see the wear on the needle or the emulsion tube. small amounts of wear have significant impact.

[Leardriver]

A properly tuned and jetted 450 will pop on decel. There is no way to get rid of it without drowning it in fuel.
The correct main jet for 2000 feet and up is a 162.

[JimDirt]

if you used carb cleaner that hit the slide you damaged your floating valve seal. so at the very least replace it. if you removed the slide verify the plate is in the correct orientation. you won't be able to see the wear on the needle or the emulsion tube. small amounts of wear have significant impact.

No i did not spray into the slide area , just inside the body where the float and jets are (in each jet orifice) , the Needle Jet i replaced was a OEM part , it should not have worn out in a year , and the symptoms dont mimic the symptoms i had when i replaced it , i would have thought the needle would show signs of discoloration or shininess or something to confirm wear , looking at it thru magnifying lenses , i found no wear at all that i could obviously see

[JimDirt]

A properly tuned and jetted 450 will pop on decel. There is no way to get rid of it without drowning it in fuel.
The correct main jet for 2000 feet and up is a 162.

I can understand a slight pop now and then , but not pop,snap,pop,pop,pop,snap,pop,pop,pop , i have a properly jetted 450X is does not pop ever , and anything i have heard that pops half as much as my R is usually found to be extremely lean , again , this is my dilemma , it acts lean , when in fact i have 1 size LARGER pilot and the fuel screw at 3+ turns , 3 turns is richer not leaner

By your account it SHOULD be "drowning" in fuel based on my jetting and fuel screw setting , yet it is lean , i cant find a blockage , and should not have to go even richer in jetting than i already am to solve the issue , i would have to go to a 65 pilot at this rate to get the fuel screw to work within the range it should , and if i go to "stock" jetting , it is even worse than it is now

I posted my issues because what would be the normal solution has not worked , and i am out of answers , and searching for something i have overlooked that has not already been listed , i am confident that the items mentioned are in good working order and have already eliminated them long before i posted , i am down to some kind of internal blockage (there has to be a reason for the 3+ turns on the fuel screw and going from a 45 to a 48 with little if any change in fuel screw adjustment , this seems to be being missed by both of you , what i am explaining is NOT a normal jetting scenario

[JimDirt]

Ken , i have a question , does a newer (like 05 for example)40mm FCR use the same air intake boot as a 41mm FCR like i have on my 02 ? , or is it not a direct bolt on without changing the intake boot to match the newer carb ? ,, or is the 40-41mm difference only internal not in the OD of the inlet/outlet ? , as i am contemplating getting a newer style FCR off EBay , as it COULD be that this 02 carb is just finally worn out or internally blocked somewhere and i might never get it to function correctly again , since i have already tried all the common solutions without any change

[Leardriver]

I have seen the area at the top of the fuel screw have some crud and buildup that restricts flow. I had to remove the screw and scrape it with a dental pick, and all of a sudden, the flow is back. Compressed air blown through there should be blasting out into the carb bell.

You are being very methodical in your approach, and you are correct, acceptable popping is a matter of experience and comparison to other bikes.

[JimDirt]

So your saying you scraped the carb body where the fuel screw O-Ring rests ?? or the screw itself ?? , if the screw , i have already had it out (to check the O-Ring) and it looks good and clean as well as the O-Ring is intact and not damaged or flattened (O-Ring,Washer,spring)

The seat area for the O-Ring looks to be clean as well , i have had the carb off the bike several times , and gave every orifice a good shot with Carb Cleaner as well as a Air blast , there was no place that it seemed blocked that i noticed , again , this is my dilemma everything appears to be clear and in good working order including the Leak Jet , A.P. and bowl vent, yet no matter what i try i get 3+ turns with richer jetting to get it to run close to what it should be , but it wont hold a idle for more than about 40 or so seconds then it will drop the idle to where if i dont hit the throttle it will die , it makes no sense at all

If i try to set the screw at 1 1/2 , it wont even start , i will kick till my leg hurts with maybe 1 pop but thats it , if i set it to 2 1/2 it will start after several kicks but pops like crazy , then the more i turn it out the less it pops but the harder it is to start again unless i hold the throttle about 1/8 open , its seriously driving me nuts !

[motosicko]

I once chased a similar problem on my wife's 06 250. Ended up being the throttle shaft. The plastic pully on the end is pinned on the shaft and it had some slop back and forth. Basically was making the slide position inconsistent and erratic. Replaced with new and fixed. Just something else to check.

[Leardriver]

Right where the oring rests there can be a corroded area.
It sounds like that is not the case with yours. It would be visable with the screw removed.

You're using a new 45 pilot?

[JimDirt]

Right now i am using a new 48 , i had a 45 in it , but it popped like crazy unless i was 3+ turns out , so i put in a 48 which should have fixed the issue and i should have been able to put the fuel screw back to 1 1/4-1/2 , but its still at 3+ turns to keep it from popping , anything less than 2 3/4 with the 48 and it pops like crazy again , but yes both jets were new , i cleaned the 45 after running it for a day without being able to get the idle/starting to work and it made no difference , so i went to the 48

[crfsonly]

remove the slide and check wear on the plate and replace the floating valve seal. if the plate is worn replace it as well. check your hot start. the plunger can corrode causing it to stay open. check the hot start nut as well. motosicko is correct...so check this as well.

ken

[JimDirt]

I am going to pull the carb off again and see if the slide or plate or seal is worn , the Hot Start i had just cleaned when i had it apart recently and it is working good and does not stick , there was just a slight residue on it , so i cleaned it off with fine steel wool , that was all that i could find wrong with the Hot Start

What would be considered excessive wear to warrant replacement ? i understand it will show some signs of wear because of the age , but where is the limit drawn ? When the slide flops around or binds up ?

Also , i can understand a worn out slide affecting the idle stability , but that still would not account for the fuel screw being 3+ turns out would it ??

I still think wherever the issue lies with the fuel screw needing to be out so far is what is affecting the idle , but i will still take it apart again and give every part a thorough going over